Clamping device for an electrical conductor



July 5, 1960 L. W. DAVISON ET AL CLAMPING DEVICE FOR AN ELECTRICAL CONDUCTOR Filed Dec.

3PM J. fiwww United States Patent Q CLAMPING DEVICE FOR AN ELECTRICAL CONDUCTOR Filed Dec. 22, 1958, Ser. No. 782,191 6 Claims. (Cl. 174-1*67) This invention relates to a device for securing conductors. More particularly this invention relates to a clamping device for securing a conductor within the bushing of an electrical apparatus.

The terminals of certain types of electrical apparatus such as transformers of the high voltage classification frequently comprise bushings which contain the conductors of the apparatus. To obtain high insulating qualities these bushings are generally of circular cross section and have a hollow substantially cylindrical interior through which a rigid conductor passes. Such bushings are generally provided with means for preventing movement of the conductor relative to the bushings. Without some type of clamping means the. conductor has a tendency to slip up or down or from side to side within the bushing. Movement of the conductor within the bushing increases the likelihood of lead breakage and electrical breakdown. Consequently, in the prior art clamping devices comprising a circular plate defining a centrally located circular aperture substantially the same diameter as theconductor have been provided for clamping the conductor. In order to prevent upward or downward movement of the conductor the aperture of such a clamping plate is sometimes threaded in order to threadedly receive the conductor. However, mounting of the clamping plate to the bushing is generally achieved by an element which is in operating engagement with the outer perimeter of the bushing. Such an arrangement causes the clamping plate to be centered with respect to the outer perimeter of the bushing. This type of arrangement is permissible if the center line of the top flange of the bushing is coaxial with the center line of s the bushings bottom flange. However, if there is any eccentricity between the top and bottom flange perimeters centering of the clamping plate with the top perimeter of the bushing will cause the insulated conductor to be moved 011? its naturally assumed centered position with respect to the bottom perimeter of the bushing. Since the rigid conductor is positioned at its lower end movement I of the conductor at its top end may cause damage to the lower positioning means. At the least there will be undesirable stresses on the lower end; Due to cost expediency the manufacturing tolerances of bushings of' the porcelain type are not very rigid and, consequently,

there is frequently eccentricity between the top and bottom perimeters of the bushings.

The device of this invention provides a means for maintaining an insulated conductor in its naturally assumed position regardless of eccentricity in the bushing."

2 insulating qualities suitable for use in high voltage electrical apparatus.

Objects and advantages other than those set forth above will be apparent from the following description when read in connection with the accompanying drawing, in which:

Fig. 1 shows a partial cross section of an eccentric bushing and expansion chamber in combination with the clamping device of this invention;

Fig. 2 is a top view of the clamping device of this invention as illustrated in Fig. l

Fig. 3 is a cross sectional view taken along lines IIIIII of Fig. 2; and

Fig. 4 is a bottom view of the clamping device of this invention as illustrated in Fig. 2.

Referring to Fig. 1 a hollow bushing 11 composed of an insulating material such as porcelain is shown encircling a conductor 12. The bushings two ends are eccentric to each other as illustrated by noncoincident center lines 15 and 20 of the top and bottom ends respectively. The particular type of bushing illustrated is generally used for the high voltage terminals of transformers. However, it is to be understood that the clamp ing device of this invention is equally suitable for bushings of other voltage classifications and for other types of hollow housings encircling conductors. Likewise the clamping device is also suitable for concentric bushings and is shown with an eccentric bushing only to illustrate the versatility of the device. Terminal end 13 of bushing 11 is of annular configuration and is encircled by 'a mounting flange 14 which is threadedly secured to the terminal end.

Conductor 12 is provided with a clamping device 16 which maintains the tube in a fixed position. The clamping device includes a circular clamping plate 17 having a diameter exceeding the inner diameter of the bushing. The plate is seated over an end of the bushing and is preferably smaller than the outer diameter of the bushing. Plate 17, as more clearly shown in Figs. 2 and 4, defines an aperture 18 which encompasses the center of the plate for receiving the conductor. Aperture 18 may be generally considered to be an elliptical or elongated slot of width barely sufficient for closely receiving the conductor and a length considerably greater than the width, preferably nearly twice the width. Spaced on opposite sides of the aperture and parallel to its elongated sides and to each other are a pair of guide tracks 19 which in the illustrated embodiment are shown as slots.

In slidable engagement with the guide slots, are a pair of gripping elements 21. The gripping elements are identical and for purposes of explanation only one will be described. Gripping element 21 is of channel shaped configuration andhas a seat member 22 extending through guide slot 19. A short leg 23 is positioned underneath the clamping, plate 17 and extends toward aperture 18 but preferably does not touch conductor 12. A longer leg 24 of the gripping element also extends toward the axis of aperture 18 in the plate and when positioned properly is substantially parallel to clamping plate 17. A portion of leg 24 describes an arcuate surface 25 having a radius substantially equal to the radius of the conductor. The two gripping elements 21 are positioned in plate 17 in a facing manner whereby the arcuate surfaces 25 define a portion of the perimeter of a circle having a radius substantially equal to the radius of the conductor for gripping the conductor therebetween. The gripping elements are provided with suitable tightening means which in the illustrated embodiment comprises a pair of bolts 26 extending through the seats 22 of the channel gripping elements and spaced on opposite sides ofthe arcuate surfaces. Nuts 28 are secured on the ends I of the bolts in order to force the gripping elements in a tight gripping relationship.

Mounted over the end of the bushing terminal and on flange 14- is a plate positioningmeans or mounting ring 29 of annular configuration and conventional expansion congruous .to the ,perimeterof the clamping plate 17.

Consequently, positioning of clamping, plate 1711s ,depend-.

out upon the position of mounting ring 29. Since mounting ring 29 is concentrically positioned with top outer perimeter .34 ofthe bushing by -mounting flange ,14 it is apparent that, therefore, clamping plate 17 is also concentric with the bushings top outer perimeter, and not necessarily with the bottom perimeter. Disposed beneath the shoulder 32 of the mounting plate andon the end of the bushing is a gasket :37 which provides a sealing relationship between the mounting plate 29 and the terminal end 13 of the bushing. v V

in assembling clamping device 16 on the eccentric bushing 11 the bushingis first installed over conductor 12. As shown in l, conductor 1-2 in its natural assumed position is. off center withrrespectto the outer perimeter of mounting flange .14. Clamping device 16 with its gripping elements 21 in a loose and expanded position is then-mounted over the conductor onto the terminal endlS of the bushing. Care is taken so that the conductor is not disturbedfrom its naturally assumed position. Clamping plate 17 is then moved with respect to slidably engaging gripping elements 21 until it appears that the clamping plate is centered with the outer perimetcr of mounting flange M. It is very likely that rotation of the clamping plate to correctly position aperture 18 will be necessary prior to centering the plate in order to receive the conductor through aperture 18 without disturbing its naturally assumed position. 7

Mounting plate 29 and expansion chamber 30 with gasket 3'? are then lowered over the conductor onto the mounting flange 14. .If clamping plate 17 does not enter ridge 33 the clamping plate must be repositioned until it is firmly seated in shoulder 32. Once the clamping plate 1'7 is properly positioned without disturbing conductor 12 the expansion chamber 30 and mounting ring 29 with gasket .37 are removed and gripping elements 21 are tightened to securely lock conductor 12 in the t-arcuatc surfaces 25. The expansion chamber and mounting ring are once again placed on the bushing, thereby completing the assembly of the bushing and cooperating parts.

By means of the above describednovel device a conductor may be securely retained in its naturally assumed position within a hollow bushing even though the bushing is eccentric. This device is particularly suitable for rigid type electrical rod conductors wheremovement of the conductor from its naturally assumedtposition is undesirable because of the stresses that would be created. The cooperation of elongated aperture 18 and gripping elements 21 provide a means for fixedly positioning the conductor concentric to plate 17 or in any of a number of positions about the plates center depending upon whatever the conductors naturally assumed position may be.

The above described clamping device is not limited to only :one diameter size of bushing. By substituting clamping plate 17 with a plate of a diameter corresponding to shot ersize ofbushing the samesize of gripping elements may be employed independently of bushing sizes. Thus, a versatile clamping device is provided which is easily convertible foryarious sizes of bushings.

Although only one embodiment of'the present invention has been illustrated and described it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims. i

What is claimed is:

1. A clamping device for adjustably clamping a conductor in a hollow housing, said device comprising: a

circular plate, said plate definingan elongated aperture for snugly receiving said conductor, and encompassing-the center ofsaid plate, guide tracks spaced on opposite Sides and parallel with the elongated portions of said aperture; a pair of gripping elements slidably engaging said guide tracks; and ti htening means cooperating with said ele ments for drawing said elements toward each other on a line perpendicular to said guide tracks in a clamping relationship with said conductor whereby said conductor is maintainedin a fixed positionin said housing;

2. A clamping device :forclamping a conductor in a hollow housing, said device comprising: a circular-plate, said plate defining an elongated aperture for snugly receiving said conductor and encompassing the center of said plate, guide tracks spaced on opposite sidesof said elongated portions of said aperture; a pairflof grippinglele mentsslidably engaging said guide tracksjand tightening meanscooperating with said elements for drawing ,said elements towardeach other on a line perpendicular. to said guide tracks in a clamping relationship witlrsaid conductor and said plate whereby said conductor ismaintained in a fixed position in said housing.

3. In combination with a hollow housing having .a longitudinallyinteriorly positioned conductor, a clamping device comprising: a circular clamping plate seated on an end of said housing, said plate defining an elongated aperture snugly encircling said conductor; a pair Iof gripping members spaced on opposite sides and parallel with the elongated portions of said aperture, said members slidably engaged with said clamping plate on a line parallel to said elongated portions, a positioning means removably mounted on said end of said housing and con centrically engaged with the outer perimeter of said housing, said positioning means having a radially inwardly extending flange overlapping said plate, whereby said plate is concentrically positioned with said .housingcnd; and tightening means cooperating with said gripping members for drawing said memberstoward each other on a line perpendicular to said elongatediportionsin a clamping relationship with said conductor whereby said conductor is maintained in a fixed position.

4. In combination with a hollow electrical apparatus bushingflhaving a longitudinally interiorly positioned conductor, a clamping devicecomprising: -a circular clamping plate seated on an end of said lbushing, said plate definingan elongated apertureforsnugly receiving said conductor in an off center position ,with respect to said plate; a pair of guide trackson said plate spaced on opposite sides of said aperture; a pair of grippingelem ents engaging said guide tracks formovement along said guide tracks in clamping association with said conductor; an

' annular positioning means removably mounted on. an}end ofsaidbushing, said positioning means having a portion overlapping said plate, whereby said plate is concentrically positioned with said bushing end; ,andaneans cooperating with said gripping elements for drawing said elements toward each other on a line perpendicular tosaid guide tracks in a clamping relationship with said plate andconductor whereby saidconductor is maintained ina fixed position.

5. In combination with a-hollow electrical apparatus bushing having a longitudinally positioned interior con- ,ductor a clamping. device comprising: a circular clamping plate seated on an end of said bushing, said plate defining an elongated aperture encompassing the, center of said plate for snugly receiving said conductorya pair of guide slots in said plate spaced on opposite sides of said aperture; a pair of channel shaped members, each said member having a channel seat removably extending through a corresponding slot with a leg positioned in the interior of said bushing slidably engaging said plate, an opposite leg of each said member external of said bushing in clamping association with said conductor; an annular positioning means removably mounted on said end of said bushing encircling said conductor, said positioning means having a radially inwardly extending flange overlapping said plate whereby said plate is concentrically positioned with said bushing end; and means cooperating with said members for drawing said members toward each other on a line perpendicular to said guide slots in a clamping relationship with said plate and conductor whereby said conductor is maintained in a fixed position.

6. In combination with a hollow electrical apparatus bushing having a longitudinally interiorly positioned insulated conductor, a clamping device comprising: a circular clamping plate seated on an end of said bushing, said plate defining an elongated aperture snugly encircling said conductor and a pair of parallel slots in said plate equidistantly spaced on opposite sides of said aperture; a pair of channel shaped members, each said member having a channel seat removably and slidably extending through a corresponding slot, a short leg of each said member positioned in the interior of said bushing in hooking engagement with the interior side of said plate, an opposite leg .of each said member having an arcuate surface in clamping association with said conductor; an annular positioning means removably mounted on said bushing end and concentrically engaged with the outer perimeter of said bushing, said positioning means having a radially inwardly extending flange seated on said bushing end, said flange having an undercut portion for receiving said plate whereby said plate is concentrically positioned with said outer perimeter of said bushing; and tightening means associated with said channel shaped members for forcing said members together on a line perpendicular to said slots in a gripping relationship with said plate and conductor whereby said conductor is maintained in a fixed position.

References Cited in the file of this patent UNITED STATES PATENTS 2,480,895 Anderson Sept. 6, 1949 FOREIGN PATENTS 655,154 Germany Jan. 10, 1938 461,681 Canada Dec. 6, 1949 

